Differential feeding success of two paralysis-inducing ticks, Rhipicephalus warburtoni and Ixodes rubicundus on sympatric small mammal species, Elephantulus myurus and Micaelamys namaquensis

Diversity and distribution of ectoparasite taxa associated with Micaelamys namaquensis (Rodentia: Muridae), an opportunistic commensal rodent species in South Africa

South Africa boasts a rich diversity of small mammals of which several are commensal and harbour parasites of zoonotic importance. However, limited information is available on the parasite diversity and distribution associated with rodents in South Africa. This is particularly relevant for Micaelamys namaquensis (Namaqua rock mouse), a regionally widespread and locally abundant species that is often commensal. To address the paucity of data, the aims of the study were to record the ectoparasite diversity associated with M. namaquensis and develop distribution maps of lice and mites associated with M. namaquensis and other rodents in South Africa. Micaelamys namaquensis individuals (n = 216) were obtained from 12 localities representing multiple biomes during 2017–2018. A total of 5591 ectoparasites representing 5 taxonomic groups – fleas, lice, mesostigmatid mites, chiggers and ticks was recorded. These consisted of at least 57 taxa of which ticks were the most speciose (20 taxa). Novel contributions include new host and locality data for several ectoparasite taxa and undescribed chigger species. Known vector species were recorded which included fleas (Ctenocephalides felis, Dinopsyllus ellobius and Xenopsylla brasiliensis) and ticks (Haemaphysalis elliptica, Rhipicephalus appendiculatus and Rhipicephalus simus). Locality records indicate within-taxon geographic differences between the 2 louse species and the 2 most abundant mite species. It is clear that M. namaquensis hosts a rich diversity of ectoparasite taxa and, as such, is an important rodent species to monitor in habitats where it occurs in close proximity to humans and domestic animals.

Ticks as Soil-Dwelling Arthropods: An Intersection Between Disease and Soil Ecology

Ticks are widespread vectors for many important medical and veterinary infections, and a better understanding of the factors that regulate their population dynamics is needed to reduce risk for humans, wildlife, and domestic animals. Most ticks, and all non-nidicolous tick species, spend only a small fraction of their lives associated with vertebrate hosts, with the remainder spent in or on soils and other substrates. Ecological studies of tick-borne disease dynamics have emphasized tick-host interactions, including host associations, burdens, and efficiencies of pathogen transmission, while under emphasizing tick biology during off-host periods. Our ability to predict spatiotemporal trends in tick-borne diseases requires more knowledge of soil ecosystems and their effect on host and tick populations. In this review, we focus on tick species of medical and veterinary concern and describe: 1) the relationships between soil factors and tick densities; 2) biotic and abiotic factors within the soil ecosystem that directly affect tick survival; 3) potential indirect effects on ticks mediated by soil ecosystem influences on their vertebrate hosts; 4) the potential for tick-mediated effects on vertebrate host populations to affect ecosystems; and 5) possible nontarget impacts of tick management on the soil ecosystem. Soils are complex ecosystem components with enormous potential to affect the survival and behavior of ticks during their off-host periods. Hence, tick-borne disease systems present an excellent opportunity for soil ecologists and public health researchers to collaborate and improve understanding of these medically important and ecologically complex disease cycles.

Complex interactions within the ectoparasite community of the eastern rock sengi (Elephantulus myurus)

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We monitored and manipulated the ectoparasite community of rock sengis over 3 years.

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We found a number of facilitating interactions between tick species.

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Inter-taxon interactions were mostly antagonistic.

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Experimental manipulation had long-term effects on the ectoparasite community.

Concomitant infection with more than one parasite species is the rule in nature. Since co-infecting parasites are exploiting the same host, interspecific interactions at the infracommunity level are likely. The nature of such interactions can be expected to affect the distribution of parasites within host populations. Intraspecific interactions within the infracommunity are not easily discernible from cross-sectional studies and the focus of most of these studies lies on relationships between endoparasitic micro- and macroparasites. In the current study of the ectoparasite community of wild eastern rock sengis (Elephantulus myurus) we experimentally reduced tick and flea infestations and monitored ectoparasite burdens over the course of three years. We found a number of within-taxon facilitating interactions between tick species that might be the result of decreasing immune responses with increasing tick burden. In contrast, inter-taxon relationships appeared to be dominated by antagonistic relationships likely to be linked to competition over feeding sites. Only one of the observed interspecific interactions was reciprocal. Our experimental manipulation revealed additional antagonistic relationships that cross-sectional studies would not have captured. In addition, we found substantial long-term changes in the sengi ectoparasite community as a result of our experimental manipulation suggesting carry-over effects of our treatment. This study is the first that evaluates interspecific interactions within the entire ectoparasite community exploiting a mammalian host in Africa and highlights the complexity of interspecific interactions within an ectoparasite community.

The Namaqua rock mouse (Micaelamys namaquensis) as a potential reservoir and host of arthropod vectors of diseases of medical and veterinary importance in South Africa

Background

The role of endemic murid rodents as hosts of arthropod vectors of diseases of medical and veterinary significance is well established in the northern hemisphere. In contrast, endemic murids are comparatively understudied as vector hosts in Africa, particularly in South Africa. Considering the great rodent diversity in South Africa, many of which may occur as human commensals, this is unwarranted.

Methods

In the current study we assessed the ectoparasite community of a widespread southern African endemic, the Namaqua rock mouse (Micaelamys namaquensis), that is known to carry Bartonella spp. and may attain pest status. We aimed to identify possible vectors of medical and/or veterinary importance which this species may harbour and explore the contributions of habitat type, season, host sex and body size on ectoparasite prevalence and abundance.

Results

Small mammal abundance was substantially lower in grasslands compared to rocky outcrops. Although the small mammal community comprised of different species in the two habitats, M. namaquensis was the most abundant species in both habitat types. From these 23 ectoparasite species from four taxa (fleas, ticks, mites and lice) were collected. However, only one flea (Xenopsylla brasiliensis) and one tick species (Haemaphysalis elliptica) have a high zoonotic potential and have been implicated as vectors for Yersinia pestis and Bartonella spp. and Rickettsia conorii, respectively. The disease status of the most commonly collected tick (Rhipicephalus distinctus) is currently unknown. Only flea burdens differed markedly between habitat types and increased with body size. With the exception of lice, all parasite taxa exhibited seasonal peaks in abundance during spring and summer.

Conclusion

M. namaquensis is the dominant small mammal species irrespective of habitat type. Despite the great ectoparasite diversity harboured by M. namaquensis, only a small number of these are known as vectors of diseases of medical and/or veterinary importance but occur at high prevalence and/or abundance. This raises concern regarding the potential of this host as an endemic reservoir for zoonotic diseases. Consequently, additional sampling throughout its distributional range and research addressing the role of M. namaquensis as a reservoir for zoonotic diseases in southern Africa is urgently needed.

Proteomics approach to the study of cattle tick adaptation to white tailed deer

Cattle ticks, Rhipicephalus (Boophilus) microplus, are a serious threat to animal health and production. Some ticks feed on a single host species while others such as R. microplus infest multiple hosts. White tailed deer (WTD) play a role in the maintenance and expansion of cattle tick populations. However, cattle ticks fed on WTD show lower weight and reproductive performance when compared to ticks fed on cattle, suggesting the existence of host factors that affect tick feeding and reproduction. To elucidate these factors, a proteomics approach was used to characterize tick and host proteins in R. microplus ticks fed on cattle and WTD. The results showed that R. microplus ticks fed on cattle have overrepresented tick proteins involved in blood digestion and reproduction when compared to ticks fed on WTD, while host proteins were differentially represented in ticks fed on cattle or WTD. Although a direct connection cannot be made between differentially represented tick and host proteins, these results suggested that differentially represented host proteins together with other host factors could be associated with higher R. microplus tick feeding and reproduction observed in ticks fed on cattle.